Agent-based computing addresses the challenges in managing distributed computing systems and networks through monitoring, communication, consensus-based decision-making and coordinated actuation. As a result, intelligent agents and multi-agent systems have demonstrated the capability to use intelligence, knowledge representation and reasoning, and other social metaphors like trust, game and institution, not only to address real-world problems in a human-like way but also to transcend human performance. This has had a transformative impact in many application domains, particularly in e-commerce, and also in planning, logistics, manufacturing, robotics, decision support, transportation, entertainment, emergency relief and disaster management, data mining and analytics. As one of the largest and still growing research fields of Computer Science, agent-based computing today remains a unique enabler of inter-, multi-and trans-disciplinary research. The International Conference on Conference on Principles and Practice of Multi-Agent Systems (PRIMA) originally started in 1998 as a regional (Asia-Pacific) workshop and in the last decade it grew to become one of the leading and influential scientific conferences for research on multi-agent systems. Each year, PRIMA brings together active researchers, developers and practitioners from both academia and industry to showcase, share and promote research in several domains, ranging from foundations of agent theory and engineering aspects of agent systems, to emerging interdisciplinary areas of agent-based research. The eighteenth edition of PRIMA took place from 26 to 30 October 2015 in Bertinoro, FC, Italy and received 94 submissions from 30 countries. From the 29 papers presented at the conference, the best theoretically-oriented ones were invited to submit an extended version for the special issue with Fundamenta Informaticae, while another special issue with the Journal of Agent-Oriented Software Engineering has been organized around the more practically-oriented papers